Mobile communication has made considerable progress in recent years. Starting from a traditional circuit switched (CS) approach as e.g. pursued in the Global System of Mobile Communication (GSM), the technological evolution has made its way towards packet switched (PS) systems such as those operating for example on the basis of the Internet Protocol (IP). Examples of such communication systems are the Universal Mobile Telecommunication Standard (UMTS) also referred to as Third Generation (3G) telecommunication system, or a system known as IMS system (IP Multimedia System), or even a network operating on the basis of the Session Initiation Protocol SIP. While in former systems, speech or voice was a main aspect of “media” as payload data to be conveyed via the communication system, nowadays all kind of media are focused on as payload, e.g. speech, music (audio), images (still images, i.e. pictures, as well as moving images, i.e. videos), executable program code, text data, and many other types or combinations of media types. The expression “media” is to be understood as not being limited to a specific type of media but is intended to be used in its broadest possible meaning.
With the emerging development of new systems, those systems coexist in parallel and interoperability is one aspect of the development. In particular in case of users represented by their terminals, e.g. mobile stations MS in GSM or user equipment UE in UMTS and/or IMS that may be illustrated/referred to also as “handsets”) that may move and/or roam throughout the communication networks, the users expect seamingless services of high quality to be provided to them, irrespective of the current communication system and/or location within one or the other of those systems in which they camp.
Services provided to users are provisioned, “at the last hop”, via access nodes. An access node in this sense is serving a user's terminal. In a roaming scenario, also commonly referred to as Handover HO, a user represented by his or her terminal, is handed over from one (currently serving) access node to a new (subsequently serving) access node (so-called target node). A selection or determination of a target node is taken based on mobility management procedures. Mobility management encompasses signaling to be exchanged between network entities. Signaling amount, however, increases with an increasing number of users in the network.
Document EP 1 429 575 proposes using lower level, i.e., L2 synch HO instead of L3 RRC and also support mass HO with mass HO command broadcast to group of users in the field of satellite communications.
Document EP 1 777 977 discloses a radio communication system enabling an inter-frequency handover for subscribers between different operators.
Document IEEE S802.16j-06/227 dated 2006 Nov. 15 proposes a group handover on a mobile relay server, MRS, based on a movement of the MRS. In such a scenario, all terminals or mobile stations served by the moving MRS are handed over.
Document EP-A1-1 058 473 discloses group handover in a cellular communications network in order to relieve congestion in an overloaded cell by handing over a group of calls to an under-loaded cell. Corresponding HO commands are sent to all terminals within a respective group.
The present invention is generally related to any cellular system where user mobility is supported. Notwithstanding this, it is particularly beneficial for so-called advanced mobile communication networks, including 3GPP Long Term Evolution (LTE) Release 8 and beyond, referred to as LTE-Advanced (LTE-A), aiming towards future ITU International Mobile Telecommunications—Advanced (IMT-A) systems where an optimized protocol overhead is required in the sense that it is optimized if kept at a minimum.
In 3GPP TR 25.913, the mobility requirement for E-UTRAN is proposed to optimize delay and packet loss during intra system handover. More specifically for E-UTRAN, Voice and other real-time services supported in the CS domain in R6 shall be supported by E-UTRAN via the PS domain with at least equal quality as supported by UTRAN (e.g. in terms of guaranteed bit rate)-over the whole of the speed range. The impact of intra E-UTRA handovers on quality (e.g. interruption time) shall be less than or equal to that provided by CS domain handovers in GERAN. The requirements on IMT-A system is under discussion at the moment, but mobility requirements are seen similar to those of E-UTRAN at least.